Diesel fuel



utented Jan. 24, 1950 STATES PATENT OFFICE G search & Development Company, Pittsburgh, Plan, a corporation of Delaware lilo Dra 1g. Application March 7, 194?,

Serial No. 733,195

6 Claims.

invention relates to improved fuels for use in internal combustion engines of the Diesel or compression-ignition type, and in particular concerns Diesel fuel compositions havin improved ignition characteristics.

In the manufacture of fuels for use in Dieseltype internal combustion engines, it has been found that many of the petroleum oil fractions whose boiling range, viscosity, and other physical characteristics render them potentially suitable for such use have improper combustion or ignition characteristics. In most cases the unsatisfactory ignition qualities take the form of too great a time lag between injection of the fuel into the cylinder and the spontaneous ignition thereof during the compression stroke, with consequent knocking, smoking, and uneven running of the engine. The extent of the time lag or ignition delay period of a fuel is conveniently evaluated :by a determination of its so-called cetane number. In brief, the cetane number of a fuel may be defined as the per cent by volume of octane in a blend of cetane and alpha-methylnaphthalene which has the same combustion characteristics as the fuel in question. A high octane number indicates a low ignition delay period, and hence better erformance as 2. Diesel fuel.

In view of the relatively low cetane numbers of most petroleum oil fractions which are otherwise suited for Diesel fuel use, it has become common practice to blend with such fractions additive materials which have the property of increasing the cetane number of the fraction. Such additives effect the desired increase in cetane number to varying degrees, but in many cases they are not satisfactory from other points of view. In some instances, for example, the additive is too expensive to be employed in quantities which effect a significant increase in the cetane number of a Diesel fuel. In other cases, the additive may be chemically unstable. In still other instances, the additive may seriously detract from some other property of the fuel, e. g., it may lower its flash point or adversely alter its viscosity characteristics, or it may impair its lubricity.

I have now found that certain sulfurized cracked distillate fractions are admirably suited for use in improving the combustion characteristics, i. e., in raising the octane number, of Diesel fuels in that they efiect a substantial and commercially significant increase in cetane number without adversely aflecting the physical characteristics of the fuel. Such sulfurized cracked distillate fractions are relatively inexpensive and are chemically stable. They are miscible with mineral hydrocarbon fuels of the Diesel type, and in the small proportions employed do not alter substantially the flash point, viscosity, lubricity, or other physical characteristics of such oils. The invention thus consists in improved Diesel til fuel compositions containing as an essential component a minor amount of a sulfurized cracked distillate fraction, the nature of which is more fully disclosed hereinafter.

The sulfurized cracked distillate fractions em-' ployed in preparing the new Diesel fuels provided by the invention are those products described by Irving E. Muskat in U. S. Patent No. 2,112,677. Such products are obtained :by heating a cracked petroleum distillate, e. g., a cracked petroleum naphtha, with elemental sulfur at term peratures above the melting point of sulfur such as temperatures from about 200 to about 300 F. and not exceeding 350 F. for several hours until a homogeneous product is obtained, and thereafter removing any unsulfurized components by distillation under vacuum. The distillation res idue is a dark colored oily liquid of medium. viscosity. It contains from about 15 to about 40 per cent by weight of sulfur in stable combined form, and is readily miscible with petroleum oils. It is usually characterized by a specific gravity of about 1.1 at F., and S. U. V. viscosity of about 400-500 at F. and about 50-60 at 210 F., and a C. C. C. flash point of about 250-280 F. While any of such sulfurized cracked distiilates may be employed in preparing the new Diesel fuel compositions, it is preferable from the standpoint of manufacturing economy to employ those containing a relatively high percentage of combined sulfur, e. g., from about 35 to about 40 per cent by weight. Such a preferred product may be prepared, for example, by heating 9. Venezuela cracked distillate having a boiling range of about 230350 F. and an A. P. I. gravity of about 50-55 with about 15 per cent by weight thereof of nowdered sulfur under partial reflux at a temperature of about 265-270 F. for about 4 hours. At the end of this period sufficient of the cracked distillate is added to replace the volume of light ends which have been distilled off. Heating and stirring is continued for an additional 24 hours, and the crude product is then distilled under a pressure of about 30 mm. t a temperature of about r 225 F. to remove unsulfurized constituents. The

distillation residue, which constitutes a preferred product for use in accordance with the present invention, is a dark oily liquid containing about 38 per cent by weight of combined sulfur and having the following physical characteristics:

Specific gravity at 60 F 1.085

Flash point, C. C. C., "F 275 Viscosity, S. U. V., at 100 F 477 Viscosity, S. U. V., at 210 F 55 The Diesel fuel compositions of the present invention may be prepared simply by blending the sulfurized cracked distillate into the fuel base in the desired proportion. Alternatively, in some instances it may be more convenient to prepare aaeaote a concentrate of the sulfurized cracked distillate in the fuel base, and thereafter blend the concentrate with a further quantity of the same or a different fuel base to secure the desired composition. Inasmuch as the sulfurized cracked distillate is completely miscible with petroleum fractions, such concentrates may be of any desired concentration, although they are ordinarily made up to contain between about 30 and about 70 per cent by weight of the sulfurized cracked distillate.

The proportion of the sulfurized cracked distillate required to secure a given degree of improvement in the ignition qualities of a Diesel fuel depends primarily upon the sulfur content of the sulfurized material and to a lesser extent upon the nature of the Diesel fuel itself. With most Diesel fuels, however, a significant increase in cetane number may be attained by employing the sulfurized cracked distillate in such an amount that the composition contains between about 0.1 and about 5.0 per cent by weight of sulfur. Accordingly, it is unusally desirable to employ a sulfurized cracked distillate having a relatively high sulfur content, i. e., 30-40 per cent by weight, although a less highly sulfurized material may be used. In general it may be said that fuels for use in light-duty Diesel engines which operate more or less intermittently will usually contain from about 1 to about 5 per cent of a sulfurized cracked distillate having a sulfur content of about 35-40 per cent by weight, whereas fuels for use in heavyduty continuously-operating engines will usually contain from about 5 to about per cent of such a sulfurized cracked distillate.

The effectiveness of the herein-described sulfurized cracked distillates in improving the ignition characteristics of a typical Diesel fuel is illustrated by the following data obtained by de termining the cetane number of compositions containing varying amounts of the sulfurized cracked distillate:

The Diesel fuel base employed was a C. R. C. secondary reference fuel having a boiling range of 370-680 F., and the sulfurized material was a sulfurized Venezuelan cracked distillate having a sulfur content of 37.8 per cent by weight. The method of testing was that described in the S. A. E. Journal, June, 1936, Page 225.

The improved Diesel fuel compositions provided by the invention may contain any of the agents commonly employed to enhance other properties of such fuels. For example, they may contain corrosion inhibitors, antioxidants, oiliness agents, detergents or dispersing agents, gum solvents, viscosity improvers, etc. The herein-described sulfurized cracked distillates do not interfere with the action of such agents, and in fact in some cases may serve to augment or even replace certain of such agents. Thus, for example, because of their extreme pressure properties, the sulfurized cracked distillates improve the lubricity of Diesel fuels and may permit dispensing with added oiliness agents. Similarly, the new fuel compositions may be prepared from any hydrocarbon fuel of the Diesel type, c. g., gas oils, residual oils, recycle stocks, shale oils, coal tar oils, hydrogenated petroleum and coal tar oils, and various paraflinic, naphthenic, or asphaltic base distillates, as well as from synthetic hydrocarbon oils such as those produced by the Fischer- Tropsch synthesis. In accordance with customary practice, the base fuel is usually blended from several types of stock to adapt it to a particular type of engine and specific operating conditions.

Other modes of applying the principle of my invention may be employed instead of those explained, change being made as regards the materials or methods herein disclosed, provided the product stated by any of the following claims, or

the equivalent of such stated product, be obtained.

I, therefore, particularly point out and dis tinctly claim as my invention:

1. An improved Diesel fuel essentially comprising a major proportion of a hydrocarbon Diesel fuel and a minor proportion of a sulfurized cracked petroleum distillate in an amount sufficient to improve substantially the ignition qualities of said fuel, said sulfurized cracked petroleum distillate containing from about 15 to about 40 per cent by weight of combined sulfur, and being obtained by a process comprising heating a cracked petroleum distillate with elemental sulfur at a reaction temperature above the melting point of sulfur but not exceeding about 350 F., and removing unsulfurized components from the resulting reaction mixture by distillation under vacuum.

2. An improved Diesel fuel essentially comprising a major proportion of a hydrocarbon Diesel fuel and a minor proportion of a sulfurized cracked petroleum distillate in an amount sufficient to improve substantially the ignition qualities of the fuel, said sulfurized cracked petroleum distillate containing from about 15 to about 40 per cent by weight of combined sulfur, and being obtained by heating a cracked petroleum distillate with elemental sulfur at a reaction temperature above the melting point of sulfur but not exceeding about 350 F.

3. An improved Diesel fuel essentially comprising a major proportion of a hydrocarbon Diesel fuel and a minor proportion of a sulfurized cracked petroleum distillate in an amount sufficient to improve substantially the ignition qualities of the fuel, said sulfurized cracked petroleum distillate containing from about 35 to about 40 per cent by weight of combined sulfur and being obtained by heating a cracked petroleum distillate with elemental sulfur at a reaction temperature between about 200 and about 350 F.

4. An improved Diesel fuel essentially comprising a major proportion of a hydrocarbon Diesel fuel and between about 0.1 and about 5.0 per cent of sulfur added in the form of a sulfurized cracked petroleum distillate having a, combined sulfur content between about 15 and about 40 per cent by weight and being obtained by heating a cracked petroleum distillate with elemental sulfur at a reaction temperature between about; 200 and about 300 F.

5. An improved Diesel fuel essentially comprising a major proportion of a hydrocarbon Diesel fuel and between about 1 and about 5 per cent by weight of a sulfurized Venezuelan cracked Detroleum distillate containing from about 35 to about 40 per cent by weight of combined sulfur and having a flash point of about 275 F., a specific gravity of about 1.1 at 60 F., and an S. U. V.

. viscosity or too-too at 1 n, and being obtained by heating a Venezuelan cracked petroleum distillate having a boiling range of 230-350 F. and an A. P. I. gravity of about 50-55 with about 15 per cent by weight of elemental sulfur at a temperature between about 265 F. and about 270 F. for about 28 hours and thereafter removing lowboiling constituents by distillation to a temperature of about 225 F. under 30 mm. pressure.

6. A composition of matter adapted to improve the Diesel ignition qualities of hydrocarbon Diesel fuels and essentially comprising a hydrocarbon Diesel fuel and between about 30 and about 70 per cent by weight of a sulfurized cracked petroieum distillate having a combined sulfur content mtween about 15 and about 40 per cent by weight REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,112,667 Muskat Mar. 29, 1938 15 2,348,080 Lincoln May 2, 1944 2,417,415 Hughes Mar. 18, 1947 wwwww @ertificate of Correction Patent No. 2,495,555 January 24, 1950 DONALD R. STEVENS It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 2, lines 25 and 52, for C. O. 0. read 0. O. 0.; column 3, line 23, for "unusally read usually;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofiice.

Signed and sealed this 23rd day of May, A. D. 1950.

THOMAS F. MURPHY;

Assistant (Jommz'asioner of Patents. 

1. AN IMPROVED DIESEL FUEL ESSENTIALLY COMPRISING A MAJOR PROPORTION OF A HYDROCARBON DIESEL FUEL AND A MINOR PROPORTION OF A SULFURIZED CRACKED PETROLEUM DISTILLATE IN AN AMOUNT SUFFICIENT TO IMPROVE SUBSTANTIALLY THE IGNITION QUALITIES OF SAID FUEL, SAID SULFURIZED CRACKED PETROLEUM DISTILLATE CONTAINING FROM ABOUT 15 TO ABOUT 40 PER CENT BY WEIGHT OF COMBINED SULFUR, AND BEING OBTAINED BY A PROCESS COMPRISING HEATING A CRACKED PETROLEUM DISTILLATE WITH ELEMENTAL SULFUR AT A REACTION TEMPERATURE ABOVE THE MELTING POINT OF SULFUR BUT NOT EXCEEDING ABOUT 350* F., AND REMOVING UNSULFURIZED COMPONENTS FROM THE RESULTING REACTION MIXTURE BY DISTILLATION UNDER VACUUM. 